[Dovecot] resilience suggestion

David Lee t.d.lee at durham.ac.uk
Wed Feb 14 17:12:58 UTC 2007

On Wed, 14 Feb 2007, Matthias Andree wrote:

> [...]
> The other important concern for a portable software as dovecot is
> portability. On some systems, temporary failure of getpwnam() is
> indistinguishable from permanent failure, thus the only solution to this
> approach is Postfix's: implement a NIS lookup client to access the
> password database to circumvent the many libc bugs lurking there.
> [...]

That sort of supports my suggestion for an option, default off and which a
site-admin would have to be explicit in turning on, to mark 'deliver'
failures as EX_TEMPFAIL.

> > We have had a source code hack since October (in "deliver.c", simply
> > replacing a "return ret" occurence with "return EX_TEMPFAIL") and it has
> > worked nicely (ported forward from rc8 towards rc22).  Mail re-queues and
> > a later delivery attempt then succeeds.
> And lingers around in the queue for a week if an account has been
> terminated? Doesn't look like a 'solution' to me.

(I hope that I never used the word 'solution' to describe it!  But it is a
workaround various real bugs in various real systems, which have had no
real resolution despite some real-long timescales.)

This EX_TEMPFAIL would be an option, default off.  If a site-admin
explicitly, consciously, opted into this changed behaviour, that possible
queue build up would, indeed be a factor to consider for such a
(non-default) choice.  For some sites, this might well be preferable to
discarding valid email.  Suppose, for instance, that rejecting valid
email adversely reflected of the company's reputation and resulted in lost
customers.  Such a site would, one hopes, be monitoring its queues anyway
for abnonmally long residencies.

(An aside, interacting with another thread: Don't let this relatively
minor suggestion delay the formalising of official version 1.0!)


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